1. Field of the Invention
The present invention relates generally to submersible pump drop pipe. More specifically, the preferred embodiment of the present invention relates to a coupling with an internally threaded portion to threadably receive one end of an externally threaded male drop pipe, and an internally non-threaded portion for receiving a non-threaded male end of a drop pipe. Using the coupling of the present invention, it is possible to connect a threaded submersible pump drop pipe to a non-threaded submersible pump drop pipe and obtain the advantages of the coupling as described herein. Further, alternative embodiments of the present invention also enable connection between two externally threaded male ends of submersible drop pipe.
2. Description of the Related Art
In water well systems, a casing pipe is inserted into the well to maintain the integrity of the well sidewalls. Once the integrity is secure, a submersible pump is placed in the well for pumping water to the surface. Attached to the pump is a drop pipe, which is the conduit that carries water from within the well to the surface. It is important in this system that the drop pipe does not leak.
For years, pipes have been joined together with couplings and sealed with an adhesive such as cement or “pipe dope” to prevent disjoinder and leaking. This practice is still used today. More recently, threaded drop pipe has been used. In fact, the most common type of drop pipe on the market today is drop pipe that has external male threads on both connecting ends. Sections of such male threaded drop pipes are connected by internally threaded female couplings.
Even more recently, drop pipe with better connections has emerged in the industry. The superior drop pipe has a female end with internal threads and a lead in section and a male end with external threads. U.S. Pat. Nos. 6,666,480 and 7,261,326 to Haney et al. are examples of this type of pipe. The male end of a first drop pipe is threaded into the female end of a second drop pipe thus eliminating the need for a coupling altogether. The advantage of the male/female threaded drop pipe is that it allows the driller to run one pipe into the well, align and screw in the next pipe with the use of only minimal amounts of pipe dope, if any, for ease of turning. Furthermore, the lead in section of the male/female threaded drop pipe provides lateral strength that is not present in traditional non-threaded drop pipe connections. The added lateral strength allows the junction of two sections of drop pipe to resist lateral forces applied to the pipe, aiding in the prevention of leaks.
Whether installing new systems or replacing damaged old ones, because the male/female threaded drop pipe offers significant advantages over traditional drop pipe, those skilled in the art seek to use it when possible. However, when replacing existing sections of drop pipe already in place, the differing types of drop pipe previously used in the industry creates a compatibility problem. If one desires to change the drop pipe in a well from the standard non-threaded drop pipe joined together by a non-threaded coupling to the male/female threaded drop pipe, the entire line of drop pipe must be replaced, resulting in an expensive conversion. Yet, a complete conversion may not be required or desired where there is only a portion or section of drop pipe that needs replacement. A similar problem is encountered if one wants to convert male threaded drop pipe joined together by a threaded coupling to the male/female threaded drop pipe.
It is therefore desirable to provide a coupling that provides the advantages of the male/female threaded drop pipe and the advantage of only requiring replacement of a desired section of the line of drop pipe in a well. It is also desirable to provide a coupling that is capable of connecting a male/female threaded drop pipe to a non-threaded drop pipe. It is a further object of the present invention to provide a coupling that is capable of connecting a male threaded drop pipe to a male/female threaded drop pipe.